The primary goal of our research program is the understanding of how the vertebrate auditory nervous system processes species-specific vocal signals and other sounds of biological significance. This research, based on our previous neurobiological studies spanning the past several years, will be conducted with various species of anurans (frogs and toads). Since we have found that their peripheral and central auditory nervous system is selectively tuned to detect signals in their vocal repertoire, we shall explore systematically the transformations that occur at each level of the auditory system. Recordings from single neurons and of evoked potentials will be conducted in the eighth nerve and in the central auditory nuclei in the medulla, midbrain, diencephalon and telencephalon of both anesthetized and freely moving animals. We believe the results of this study will provide needed insight into similar questions of sensory encoding of complex sounds at the level of single cells and populations of cells in higher vertebrate species, and that this work will serve as a model for fundamental processes underlying the neural basis for hearing and speech perception in humans.